Found this while searching - https://farside.link/redlib/r/roblox/comments/1qbxvf9/working/_on/_a/_roblox/_alternative/_its/_open/_source/
Edit: they have a CodeBerg (based on ForgeJoe) org, former link: https://github.com/orgs/OkutuProject/repositories
Federated games? Is it like servers talking to each other to show each other on the list, in this case?